[Hooman]

Hi,
I am working on a case with a flexible cylinder with a flow of air inside and a cross flow of water. This is a fluid structure interaction case and the case is such that I can define the natural frequency of the air inside the cylinder and that would then be used to solve the structure equation (ma+cv+kx=f). I am meant to change the inlet velocity of water and investigate the damping ratio and frequency of the vibrating cylinder.
I am confused as how to evaluate the frequency of the vibrating cylinder cylinder, which equations can I use to evaluate this frequency? Would that need to be evaluated using using the fluid added mas effects, etc.
I would appreciate any hints if you have come across a similar case.
Thanks,
H